I'm currently breastfeeding my 8-month-old. I've lost about 40 pounds since I had her in January.
The breastfeeding does help (it adds about 500 to your required calories, so I was able to lose weight on 1800-2000 kcal/day instead of my usual 1300-1500), but it also means kind of walking a tightrope between low enough calories to lose weight and high enough calories to maintain your milk supply. For the first six months, I had to watch my intake VERY closely. If I ate over 2000 calories per day, I wouldn't lose weight, but if I went under 1800, my milk would shut off and I'd have a hungry baby. Exercising too much (like more than an hour a day, or anything in extremely high heat) shut off the milk, too. Now that she's eating solids too, though, I can be a bit more flexible about lowering calories or exercising more without damaging the milk supply.
I'm pretty experienced with the breastfeeding + weight loss thing by now (8 months with her, and 2 years breastfeeding my older kid, with about fifty pounds lost during the first year of that), so if you've got any questions, I'd be happy to try to help.
Former maintainer, now losing again in 2014 after my second baby.